This invention relates to the treatment of allergies, and more specifically to immunotherapy by administration of allergenic extracts by the oral route as an alternative to injection therapy.
Unusual susceptibility or hypersensitivity in humans to any offending substance is commonly termed an "allergy", and the offending substance is termed an "allergen". Concentrated solutions of allergens used for diagnosis or treatment of allergic disease are known as "allergenic extracts".
Types of allergy have been divided into four subdivisions based on type of reaction. The simplest reaction, called a Type I or anaphylactic reaction, is the category into which most cases of simple allergy fall. These cases include seasonal rhinitis or hay fever, stinging insect bite, some food and drug allergies, extrinsic bronchial asthma, and some cases of urticaria. The present invention relates to this type of allergy.
A Type I reaction is mediated by a group of antibodies known as "reagins" or skin-sensitizing antibodies, and these are designated by the symbol IgE. Reagin may circulate in the serum or bind to certain cells. When antigen in the form of an allergen reacts with this cell-bound reagin, certain substances, among them histamine, are believed to be released, and the familiar allergic or atopic reaction occurs.
Immunotherapy has been a mainstay in the treatment of hypersensitivity for many years. Long before the true nature of Type I, IgE mediated hypersensitivity was elucidated, immunotherapy was accepted by the medical community as a means for ameliorating allergic symptoms.
The mechanism for relief of allergy symptoms with this form of treatment is not entirely clear. It has been shown that there is both a reduction of allergen-specific IgE antibody levels to the administered allergen with time, as well as a rise in specific IgG, the so-called bocking antibody. The decreased IgE level reduces the patient's "sensitivity", possibly through the activation of suppressor T-cell activity, which inhibits specific IgE release from plasma cells. The enhanced IgG level appears to prevent coating of the mast cell surface by IgE, thus blocking receptor sites of the IgE molecules and inhibiting the events that would lead to release of chemical mediators of local allergic symptoms.
Formerly referred to as "desensitization", but currently more correctly referred to as "hyposensitization", immunotherapy has been used for the remediation of allergic symtoms resulting from all classes of allergens such as inhalants, injectants, contactants and ingestants.
Most commonly, allergic immunotherapy is employed in cases in which a patient has a history suggesting an allergic condition, and has a significantly positive allergy skin test to one or more specific allergens. Treatment involves the injection of graduated doses of the specific allergenic extracts to which the patient has been found to be sensitive, followed by maintenance doses of the highest concentrations of extracts tolerated by the patient that relieves symptoms without producing undesirable local or general reactions. The size of this dose and the interval between doses can be adjusted as necessary. The interval between doses may in some instances be increased from one week or less to as long as four weeks, but protection is usually lost rapidly if the interval is more than four weeks,
At least a 50 percent reduction in symptoms should be expected in most patients after one to two years of immunotherapy with an extract of the specific allergen or allergens.
As with any injection of a foreign substance, or antigen, there is always a risk of local reaction, and occasionally systemic reactions to these biologically potent materials may occur. In certain individuals, systemic reactions may be life-threatening. Accordingly, caution must be used in determining the rate of dosage increase, and patients should be carefully observed following injection treatment.
Extensive literature over the past several decades confirms the utility of hyposensitization by hypodermic injection of allergenic extracts in the treatment of specific allergies. However, despite improvements in quality of the extracts and reduction in the number and severity of side-effects, the treatment is still very demanding on both patient and doctor, requiring many visits, 20 to 30 minutes observation after each injection, and continued risk of systemic reactions. Treatment has also been more effective for certain classes of allergens than for others, which may be an attribute of the route of administration.
Oral immunotherapy as an alternative to injection therapy may, under the proper conditions, provide a treatment which is at least equally as effective, while eliminating some of the negative and often traumatic aspects of injection therapy. Published papers have shown minimum side-effects and few systemic reactions from this form of treatment, even when doses of allergen or allergenic extracts significantly higher than those used for injection therapy were administered. Treatment was done entirely in the home, as is common with other oral medication. Patients did not miss school or work, and transportation expenses for professional administration were minimized. The traumatic aspects of hypodermic injections, particularly with children, were likewise eliminated. Effective oral immunotherapy could, therefore, represent an inexpensive and safe form of allergy treatment which my also broaden the range of effectiveness.